Impact of Intra-Shift Napping on EMS Cardiovascular Health

University of Pittsburgh

Status: Completed

Conditions: Heart Rate Variability; Blood Pressure

Treatments: Behavioral: Intra-Shift Napping

Study type: Interventional

Funder types: Other

Identifiers

NCT04469803

STUDY19120222

Details and patient eligibility

About

Cardiovascular disease (CVD) exerts a significant health burden among shift workers, including police, firefighters, and emergency medical services (EMS). The unique occupational demands inherent to these professions--sleep loss, circadian misalignment, high stress, and sustained hyper-vigilance--confer increased risk for both on and off-duty cardiovascular events. Mitigating cardiovascular risks in these professions requires that we first identify robust markers and potential mechanisms of risk. Previous work suggest shift work has a negative impact on blood pressure (BP) and heart rate variability (HRV). Blunted BP dipping at night and during sleep, and reduced HRV are powerful markers of increased CVD risk. Both are linked to preclinical indicators of cardiac damage, such as presence of coronary artery calcium, left atrial enlargement, and cardiovascular-related mortality. This study will use an experimental crossover study design with three intervention conditions to test the impact of a 30 minute brief nap and a 2-hour longer nap versus no nap on BP and HRV. Outcomes of interest include blunted dipping of BP during nighttime hours and during sleep and HRV.

Full description

Cardiovascular disease (CVD) exerts a significant health burden among shift workers, including police, firefighters, and emergency medical services (EMS). The unique occupational demands inherent to these professions--sleep loss, circadian misalignment, high stress, and sustained hyper-vigilance--confer increased risk for both on and off-duty cardiovascular events. Mitigating cardiovascular risks in these professions requires that we first identify robust markers and potential mechanisms of risk. Previous work suggest shift work has a negative impact on blood pressure (BP) and heart rate variability (HRV). Blunted BP dipping at night and during sleep, and reduced HRV are powerful markers of increased CVD risk. Both are linked to preclinical indicators of cardiac damage, such as presence of coronary artery calcium, left atrial enlargement, and cardiovascular-related mortality.

Critical questions remain:

Are BP dipping and HRV impacted by napping during night shift work? Compared to those who do not nap, does napping during night shifts help BP and HRV to normalize quicker in the hours immediately post night shift work? What is the impact of brief naps (e.g., 30 minutes) versus longer naps (e.g., 2 hours)?

This study will use a randomized crossover experimental design of EMS workers and be based in the laboratory environment. Participants will complete three intervention conditions. All study arms will involve a 12-hour simulated night shift. The intervention of interest is napping (no nap vs. a 30 minute nap vs. a two-hour nap) in a randomized crossover study design. The primary outcome of interest is BP dipping (>10% drop) and Heart Rate Variability (HRV) measured as the standard deviation of inter-beat intervals of the sinus beats in milliseconds (SDNN). All outcomes will be measured serially before the simulation, during simulated night shifts, during the intra-shift napping period, and during recovery.

Enrollment: 28 patients

Sex: All

Ages: 18 to 100 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

1. age 18 years or older;
2. current / active certification as an EMS clinician at the EMT-Basic, Advanced, Paramedic, Flight Paramedic, or Flight Nurse level, or healthcare shift worker;
3. has not ever been diagnosed with any of the following: hypertension, cardiovascular disease, myocardial infarction, stroke/TIA, chronic kidney disease, adrenal disease, thyroid disease, rheumatologic disease, hematologic disease, cancer of any type, dementia/memory loss, organ transplantation; insomnia or other major sleep problem; sleep apnea or other diagnosis that is related to problems with breathing or the airway; and
4. is not currently pregnant.

Exclusion criteria

1. 17 years of age or younger;
2. not an EMS clinician or inactive as an EMS clinician or not a healthcare shift worker;
3. has ever been diagnosed with hypertension, cardiovascular disease, myocardial infarction, stroke/TIA, chronic kidney disease, adrenal disease, thyroid disease, rheumatologic disease, hematologic disease, cancer of any type, dementia/memory loss, organ transplantation; insomnia or other major sleep problem; sleep apnea or other diagnosis that is related to problems with breathing or the airway;
4. is currently pregnant;
5. is unwilling to wear multiple monitoring devices (e.g., automated blood pressure monitoring device, holter monitor for HRV measurement, wrist actigraphy) for the duration of the study protocol.
6. is unwilling to refrain from caffeine during the study protocol; or
7. is unwilling to adhere to sleep / wake times outlined in the study protocol.

Trial design

Primary purpose: Other

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: None (Open label)

---

28 participants in 6 patient groups

No nap, brief nap, then longer nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with no nap first, undergo a 1-week minimum washout, then complete the protocol again with a brief nap, then undergo a minimum 1-week washout, then return to complete the protocol again with a longer nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping

No nap, longer nap, then brief nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with no nap first, undergo a 1-week minimum washout, then complete the protocol again with a longer nap, then undergo a minimum 1-week washout, then return to complete the protocol again with a brief nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping

Brief nap, no nap, then longer nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with brief nap first, undergo a 1-week minimum washout, then complete the protocol again with no nap, then undergo a minimum 1-week washout, then return to complete the protocol again with a longer nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping

Brief nap, longer nap, then no nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with brief nap first, undergo a 1-week minimum washout, then complete the protocol again with longer nap, then undergo a minimum 1-week washout, then return to complete the protocol again with no nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping

Longer nap, brief nap, then no nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with a longer nap first, undergo a 1-week minimum washout, then complete the protocol again with a brief nap, then undergo a minimum 1-week washout, then return to complete the protocol again with no nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping

Longer nap, no nap, then brief nap

Experimental group

Description:

Participants will be monitored for 72 total hours, including a 12-hour simulated night shift. At baseline (consent), participants randomized to crossover study design with three study arms (No nap, brief nap, longer nap). In this sequence, participants will perform the 12-hour night shift with a longer nap first, undergo a 1-week minimum washout, then complete the protocol again with no nap, then undergo a minimum 1-week washout, then return to complete the protocol again with a brief nap opportunity.

Treatment:

Behavioral: Intra-Shift Napping